Crystal violet composition



CRYSTAL VIOLET COIVIPOSITION Wallace G. Clarke, Rensselaer, and Walter G. Drautz, Glenmont, N. Y.

No Drawing. Application April 29 1953, Serial No. 352,019

8 Claims. (Cl. 106-145) This invention relates to a method for producing an improved Crystal Violet, and compositions containing same.

Crystal Violet, color index No. 681, is a dyestuif which is widely used in carbon paper and hectograph compositions in which it is employed in combination with other shading colors which blend to a shade approaching black. As ordinarily obtained, Crystal Violet has a moisture content of about 4 per cent or more which is not the optimum condition for use since the relatively high viscosity of its aqueous dispersion is objectionable. Several methods have been resorted to in order to decrease the moisture content as for example, by use of a vacuum, or solvent methods. However, solvent drying is a complicated, expensive and dangerous method, while vacuum drying is a tedious and lengthy operation in which the dyestufi crystals tend to change form whereby their coloring characteristics are affected. This is particularly important when dealing with hectograph dyestuif compositions containing Crystal Violet. An acceptable black hectograph ink must be capable of printing a great many, as for example, 150 to 200, copies in a good deep black shade from a single master copy, and the last print made should not differ greatly in shade from the first print. The proportions of the proper shading dyestuifs therein must be carefully controlled in order to achieve the desired results. If the characteristics of any one of the colors employed in the composition are altered, the hectograph color will be thrown out of balance and any ink containing same will be inferior with respect to shade, number of duplicates to be obtained therefrom, stability in storage, and the like.

We have now found that improved results may be obtained by subjecting aqueous dispersions comprising Crystal Violet to an atmospheric drum drying operation to yield a product having a moisture content of less than about 2 per cent. The resulting product is valuable in that the material has been subjected to heat in the drying operation for such a short time that the crystals have had no opportunity to change form. The high degree of dryness of the resulting product makes it possible to produce very low viscosity compositions, particularly hectograph compositions containing a black dyestutf mixture comprising Crystal Violet in an ink vehicle.

This drying process is advantageous when employed with Crystal Violet alone and also with dyestufi mixtures in which Crystal Violet is employed in proportions of at least 30 per cent by weight. For example, a hectograph black dyestuff composition comprising a mixture of 35 to 45 parts by weight of Crystal Violet, 40 to 45 parts by weight of Chrysoidine (C. I. 20) and 15 to 20 parts by weight of Rhoduline Blue (C. I. 658) is greatly improved when subjected to a drum drying operation in accordance with this invention in that a decreased viscosity is obtained when the composition is mixed with the hectograph dope vehicle, and a more uniform shade is produced. Ordinary drying of such a composition at high temperatures would tend to change the shade, yielding hectograph prints that are not a true black. The aforementioned hectograph States Patent i 2,752,255 Patented June 26, 1956 composition containing Crystal Violet, Chrysoidine and Rhoduline Blue is described and claimed in copending application Serial No. 352,020, filed on even date herewith, by Walter G. Drautz.

In carrying out the process of this invention, an aqueous dispersion, which is in the form of a suspension or slurry containing 40 to per cent solids, of which Crystal Violet comprises at least 30 per cent, is passed on an ordinary atmospheric rotary drum drier, or similar moving surface, heated to temperatures of about 270 to 360 F., preferably from about 320 to 345 F. These temperatures may be obtained by maintaining the steam pressure in the drum drier at about 30 to 130 pounds per square inch gauge, preferably about 80 to 110 pounds per square inch gauge. Other heating means may, of course, be employed.

The composition is allowed to remain on the heated surface for a relatively short period of time, less than one revolution, being usually about 5 to 30 seconds. The duration of exposure to the evaporating conditions of the drier will, of course, depend upon the size of the drum and the speed of rotation. With the ordinary atmospheric drum driers, speeds of the order of about 4 to 5 R. P. M. are usually maintained.

The dried product is scraped ofi as a powder having a moisture content of about 1 to 2 per cent and improved characteristics with respect to viscosity, stability, shade, and the like.

When a hectograph dye mixture comprising Crystal Violet is treated in accordance with this invention, the product may be incorporated into any suitable hectograph ink vehicle or dope. Such vehicles may comprise carnauba wax, weeswax, mineral oil, lanolin, Vaseline, lard oil, lecithin or oleic acid. For example, one effective method of making a suitable hectograph coating composition is to melt a wax, such as beeswax, and then add oleostearine, mutton tallow or lard oil, or other suitable greasy or oily substance. A dye mixture containing Crystal Violet is added to this mixture and then cooled, and ground at elevated temperatures to produce a uniform low viscosity paste-like mass in which the dye particles are intimately dispersed. This mass is readily melted and flowed or otherwise applied as a coating on a suitable carrier.

The following examples, in which parts are by weight are illustrative of the process of the instant invention and are not to be regarded as limitative.

Example 1 A slurry of Crystal Violet, about 70 per cent solids content by weight, is passed on an atmospheric rotary drum drier heated with steam at a pressure of 80 to pounds per square inch gauge and operated at 4 R. P. M. After one revolution, the dried product is scraped ofi? as a powder having a moisture content of about 1.5 to 2 per cent.

In each of the above examples, 2 to 5, the dyes were mixed in the amounts given, and the resulting mixture dispersed in the form of a suspension or slurry in an equal amount of Water with stirring for half an hour at about C. The slurry was then passed on an atmospheric rotary drum drier heated with steam at a pressure of 95 pounds per square inch gauge and operated at 4 to 5 R. P. M. The dried product is scraped ofi as a black powder highly suitable for producing low viscosity hectograph ink compositions.

Various modifications and variations of this invention n will be obvious to persons skilled in the art and it is to be understood that such modifications and variations are to be included within the purview of this application and the spirit and scope of the appended claims.

We claim:

1. A process for the production of a hectograph'dyc mixture containing Crystal Violet comprising applying a layer of an aqueous dispersion containing about '40 to 80% of solids, at least 30% of which is Crystal Violet, to a moving surface heated sufiiciently to reduce the moisture content of the dispersion to less than about 2% Within a period of about 5 to seconds, and within such period, removing the dried product from said surface as a powder having a moisture content of less than about 2%.

2. A process as defined in claim 1 wherein said surface is heated to a temperature of about 270 to 360 F.

3. A process as defined in claim 2 wherein said surface is the surface of a revolving atmospheric rotary drum drier.

4. A process for the production of a hectograph dye mixture comprising applying a layer of an aqueous dispersion containing about 40 to 80% of solids, said solids consisting essentially, by weight, of about to 45 parts of Crystal Violet, to parts of Chrysoidine, and 15 to 20 parts of Rhoduline Blue, to a moving surface heated sufiiciently to reduce the moisture content of the dispersion to less than about 2% within a period of about S'tO 30 seconds, and within such period, removing the dried 4: product from said surface as a powder having a moisture content of less than about 2% 5. A process as defined in claim 4 wherein said surface References Cited in the file of this patent UNITED STATES PATENTS 1,222,062 Bent et a]. Apr. 10, 1917 1,812,802 Price June 30,1931 2,281,807 Shinn May 5, 1942 2,461,896 Herrick Feb. 15, 1949 2,492,163 Locke Dec. 27, 1949 2,586,570 Skiles Feb. 19, 1952 2,684,908 Drautz July 27, 1954 GT HER REFERENCES Perry: Chemical Engineers Handbook (1950), pp. 863-6. 

1. A PROCESS FOR THE PRODUCTION OF A HECTOGRAPH DYE MIXTURE CONTAINING CRYSTAL VIOLET COMPRISING APPLYING A LAYER OF AN AQUEOUS DISPERSION CONTAINING ABOUT 40 TO 80% OF SOLIDS, AT LEAST 30% OF WHICH IS CRYSTAL VIOLET, TO A MOVING SURFACE HEATED SUFFICIENTLY TO REDUCE THE MOISTURE CONTENT OF THE DISPERSION TO LESS THAN ABOUT 2% WITHIN A PERIOD OF ABOUT 5 TO 30 SECONDS, AND WITHIN SUCH PERIOD, REMOVING THE DRIED PRODUCT FROM SAID SURFACE AS A POWDER HAVING A MOISTURE CONTENT OF LESS THAN ABOUT 2%. 